Conventional latches are used to restrain the movement of one member or element with respect to another. For example, conventional door latches restrain the movement of a door with respect to a surrounding door frame. The function of such latches is to hold the door secure within the frame until the latch is released and the door is free to open. Existing latches typically have mechanical connections linking the latch to actuation elements such as handles which can be actuated by a user to release the latch. Movement of the actuation elements is transferred through the mechanical connections and will cause the latch to release. The mechanical connections can be one or more rods, cables, or other suitable elements or devices. Although the following discussion is with reference to door latches (e.g., especially for vehicle doors) for purposes of example and discussion only, the background information provided applies equally to a wide variety of latches used in other applications.
Most current vehicle door latches contain a restraint mechanism for preventing the release of the latch without proper authorization. When in a locked state, the restraint mechanism blocks or impedes the mechanical connection between a user-operable handle (or other door opening device) and a latch release mechanism, thereby locking the door. Many conventional door latches also have two or more lock states, such as unlocked, locked, child locked, and dead locked states. Inputs to the latch for controlling the lock states of the latch can be mechanical, electrical, or parallel mechanical and electrical inputs. For example, by the turn of a user's key, a cylinder lock can mechanically move the restraint mechanism, thereby unlocking the latch. As another example, cable or rod elements connecting a door handle to the latch release mechanism can be controlled by one or more electrical power actuators. These actuators, sometimes called “power locks” can use electrical motors or solenoids as the force generator to change between locked and unlocked states.
A number of problems exist, however, in the conventional door latches described above. For example, conventional restraint mechanisms in such latches are typically quite complex, with numerous parts often having relatively complicated movements. Such latches are thus more expensive to manufacture, assemble, maintain, and repair. This problem is compounded in latches having multiple lock states as mentioned above. These latches often require separate sets of elements corresponding to and controlling each lock state of the latch.
In addition, because conventional door latches are typically relatively complex (especially latches having multiple lock states), the ability of a latch design to be used in diverse applications suffers significantly. For example, many conventional door latches are suitable for installation in a particular door, but cannot readily be installed in other door designs. As another example, door latch applications in which only limited latching functions are needed generally call for a different door latch than door latch applications in which full latching functions are needed. Conventional door latches are far from being “universal” (capable of installation in a number of different applications and easily adaptable to applications varying in functionality). Therefore, it is often necessary for a manufacturer, installer, or servicer of door latches to keep a wide variety of different door latches in inventory—an expensive and inefficient practice.
Space and location constraints for door latches varies significantly from application to application. In some applications for example, connecting rods are used to mechanically link door handles or user-operable lock buttons to the latch, while in other applications bowden cables are more suitable. As used herein and in the appended claims, the terms “user-operable”, “user-actuatable”, and the like include direct and indirect user operation and actuation. Therefore, devices or elements described in such manner include those that are operated upon or actuated indirectly by a user in some manner (e.g., via electronic actuation, mechanical linkage, and the like), and are not necessarily limited to devices or elements intended for direct contact and manipulation by a user in normal operations of the latch.
The latch space and location constraints mentioned above can also require latch connections to be made only from certain sides or the latch or only at certain angles with respect to portions of the latch. Conventional latch manufacturers address such problems by providing specialized latches for specific applications or groups of applications. Once again, this solution requires a manufacturer, installer, or servicer of door latches to incur the expense of keeping a wide variety of different door latches in inventory.
For obvious reasons, increased latch complexity also has a significant impact upon assembly and repair cost. Conventional door latches are generally difficult to assemble and require a significant amount of assembly time. An assembler must often orient the latch assembly in several directions during the assembly process (i.e., flip the latch over or turn the latch repeatedly). Also, the large number of small and intricate parts typically used in conventional door latches adds to assembly cost. Particularly in light of the specialized nature, function, and redundancy of many door latch parts, conventional door latches designs are far from being optimized.
Problems of latch weight and size are related to the problem of latch complexity. The inclusion of more elements and more complex mechanisms within the latch generally undesirably increases the size and weight of the latch. In virtually all vehicle applications, weight and size of any component is a concern. Additionally, increased weight and size of elements and assemblies within the latch necessarily requires more power and greater force to operate the latch. Because power is also at a premium in many applications (especially in vehicular applications), numerous elements and complex assemblies within conventional door latches are an inefficiency that is often wrongly ignored. Not only are larger and more complex latches a power drain, but such latches are typically unnecessarily slow.
Latch operating speed continues to be important to the latch design viability, particularly with the increasingly common use of electromechanical assemblies in many latch applications. The time required to perform each latch operation has been reduced to well under one second in vehicular applications, and significant advantages exist for reducing such time even further. Specifically, it is most desirable to reduce the amount of time to change the state of a latch, such as from a locked state to an unlocked state, from a child-locked state to an unlocked state, etc. Although numerous conventional mechanisms exist for accelerating latch state changes, the speed at which such changes are performed remains far from optimal. This is due at least in part to the incremental improvement of conventional mechanical assemblies in lieu of using significantly different mechanisms and devices for changing latch states. Also, compact actuation devices capable of very rapidly and significantly changing the state of a mechanical assembly are not common. Such actuation devices that do exist are often not suitable for use in mechanical devices having moving and inertial forces that are significantly larger than the actuation device itself (as is the case with many types of latches).
Another problem with conventional door latches relates to their operation. Particularly where a latch has multiple lock states, the ability of a user to easily and fully control the latch in its various lock states is quite limited. For example, many latches having a child locked state (i.e., the inside door handle is disabled but the outside door handle is not) require a user to manually set the child locked state by manipulating a lever or other device on the latch. Other latches do not permit the door to enter a dead locked state (i.e., both the inside and outside door handles being disabled). Also, conventional door latches generally do not permit a user to place the door latch in all lock states remotely, such as by a button or buttons on a key fob. These examples are only some of the shortcomings in existing door latch operability.
Still another problem of conventional door latches is related to power locks. The design of existing power lock systems has until now significantly limited the safety of the latch. Latch design limitations exist in conventional latches to ensure, for example, that dead locked latches operated by powered devices or systems will reliably unlock in the event of power interruption or failure. Such limitations have resulted in latch designs which permit less than optimal user operability. Although manual overrides for conventional door latches do exist, these overrides typically add a significant amount of complexity to the door latch and are difficult to install and assemble. Therefore, a reliable design having a failure mode and a simple manual override for an electrically powered latch which is electrically actuatable in all locked states remains an elusive goal.
In conventional door latches, yet another problem is caused by the fact that an unauthorized user can often manipulate the restraint mechanism within the latch and/or the connections of the latch to the door locks to unlock the latch. Because conventional door latches typically have at least some type of mechanical linkage from the user-operable elements (e.g., lock cylinders) to the restraint mechanism in the latch, the ability of an unauthorized user to unlock the latch as just described has been a persistent problem. Many existing door latches have multiple paths through which force is transmitted from a user-operable device to the restraint mechanism in the latch. For example, where the restraint mechanism is a ratchet selectively held in a locked position by a movable pawl, conventional door latches have multiple direct and/or indirect connections to the pawl from multiple user-operable devices. Each such connection added to a latch assembly provides another latch input that is subject to manipulation by an unauthorized user to unlock the latch. Although multiple connections are necessary to full latch functionality, many existing latch designs employ separate and independent connections without regard for the ability to reduce the number of force transmitting paths into the latch.
As described above, inputs to latch assemblies typically include one or more user-operable devices such as handles, buttons, levers, and the like for releasing the latch restraint mechanism and one or more user-operable devices such as lock cylinders, sill buttons, and the like for changing the lock state of the latch. The conventional practice of employing separate connections to the latch for such inputs increases latch complexity, weight, and expense, and increases the design difficulty in selectively disabling or isolating any particular input as desired.
Another shortcoming of conventional latch assemblies involves the inability of conventional door locks to correctly respond to more than one latch assembly input at one time. In a well-recognized example, conventional vehicle door latches having a power unlock feature typically require one or more electrical signals to trigger a change of state in the latch (e.g., from a locked state to an unlocked state) before actuation of a handle or other user-manipulatable device will unlatch the latch. If a user actuates the handle before the latch has changed states, this actuation can require the user to release and re-actuate the handle, and can even prevent the latch from changing between its locked and unlocked states. At best, either result is an annoying attribute that remains unaddressed in conventional latch assembly designs. In this and other examples, a conventional latch assembly is unable to respond to actuation of more than one input at a time, or is only responsive to one of two inputs actuated simultaneously or closely in time.
A number of existing latch assembly designs provide for elements or devices that can be powered to change the locked or unlocked state of the latch assembly. Some latch assemblies even have elements or devices that can be powered to drive the latch assembly into a latched state. However, due at least in part to safety issues, conventional latch assemblies do not have elements or devices that are powered for unlatching the latch assembly. Such latch assemblies are not designed with protection against inadvertent or accidental latch release in mind, and do not provide any mechanism by which powered unlatching can be reliably employed. As such, full functionality of conventional latch assemblies is significantly limited.
In light of the problems and limitations of the prior art described above, a need exists for a latch assembly which can be used in many applications, is modular and which therefore has easily adaptable functionality to meet the needs of a large number of applications (i.e., from limited to full functionality), has the fewest elements and assemblies possible, is smaller, faster, and lighter than existing latches, consumes less power in operation, is less expensive and easier to manufacture, assemble, maintain, and repair, provides a high degree of flexibility in user operation to control the lock states of the latch, is capable of properly responding to concurrent or nearly concurrent actuation of multiple latch assembly inputs, can be powered to an unlatched state responsive to actuation of more than one input to the latch assembly actuated concurrently or nearly concurrently, has a simple and reliable design for manual override in the event of power interruption or failure, offers improved security against unlocking by an unauthorized user, has as few inputs as possible for unlatching the latch while still retaining full latch functionality, and provides the ability to quickly isolate desired combinations of latch inputs. A need also exists for an actuation device that is compact, fast, capable of rapidly changing the states of a mechanical device (such as a latch), and is operable significantly independent of the size of device input and inertial forces. Each preferred embodiment of the present invention achieves one or more of these results.